In a work vehicle equipped with a so-called Hydrostatic transmission (HST) circuit, a hydraulic pump is driven by an engine, and hydraulic fluid discharged from the hydraulic pump is supplied to a hydraulic motor. A drive wheel is then driven by the hydraulic motor, propelling the vehicle forward.
As a conventional example of a work vehicle such as that described above, a work vehicle such as that described in Japanese Laid-Open Patent Application Publication No. 2004-144254 is known in which the displacement of the hydraulic motor is electronically controlled. This work vehicle has a hydraulic motor, a cylinder, and a control valve. The cylinder has a main cylinder body and a piston rod that extends and contracts with respect to the main cylinder body, and the angle of an inclined shaft of the hydraulic motor, i.e., its tilt angle, is changed through the movement of this piston rod. The piston rod is connected to the control valve. The control valve is an electromagnetic control valve that is electronically controlled by the controller. Thus, in this work vehicle, it is possible to change the displacement of the hydraulic motor as desired by controlling the cylinder through electronic control of the control valve.